Conventionally, while using an X-ray diagnosis apparatus, when an X-ray pulse is radiated onto an examined subject (hereinafter, “patient”) P, it may be observed that the descending waveform of the pulse has a gradual descent. Such a gradually-descending waveform (hereinafter, “wave tail”) not only makes no contribution to the imaging process, but also causes unnecessary radiation exposure for the patient P. It is known that the lower the output level of an X-ray pulse is, the more easily a wave tail occurs. For this reason, during a fluoroscopy process, which has a lower output level than an image taking process, a technique called grid control is used by which wave tails are eliminated (cut off) by applying a voltage to a grid of the X-ray tube and inhibiting thermal electrons from being released.